Method of converting solid carbon dioxide to gaseous form and apparatus therefor



Patented Oct. 19, 1937 v UNITED STATES PATENT OFFICE METHOD OF CONVERTING SOLID CMN DIOXIDE T0 GASEOUS FORM AND AP- PARATUS THEREFOR taneously after the process isinitiated, thus par-' ticularly adapting the same for use in replenishing the supply of gaseous carbon dioxide in a refrigerating system, for example, where the replenishing operation must be consummated with great rapidity.

A more specific object of the invention is toprovide an. improved method of changing solid.

4 carbon dioxide to gaseous form in which a portion.

of hot compressed gaseous carbon dioxide is circulated in heat exchange relation with a confined quantity of solid carbon dioxide .to convert the latter into gaseous form at a'relatively high pressure.

Another object of the invention is to provide a novel apparatus for circulating hot gaseous carbon dioxide in heat exchange relation with a portion of solid carbon dioxide to convert the latter quickly and 'efliciently into gaseous carbon dioxide.

A further object ofthe invention is to provide a refrigerating apparatus in which gaseous carbon dioxide is successively compressed, condensed Y and evaporated and including an improved arrangement for replenishing the charge'of gaseous carbon dioxide at will from a source of solid carbon dioxide.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty .which characterize the invention are pointed out withparticularity in the claims annexed to and forming a part of this specification.

' For a better understanding of the invention, reference may be had to the accompanying drawing in which the single figure is a diagrammatic representation of a refrigerating apparatus embodying the present invention.

Referring more particularly to the drawing. a preferred apparatus has been illustrated for carrying out the improved method of converting solid carbon dioxide to gaseous carbon dioxide contemplated by the present invention. In general, this method includes as its primary step the circulation of hot gaseouscarbon dioxide in heat exchange relation with a portion of solid carbon form. When the solid carbon dioxide is used as a source'for replenishing the supply or charge of gaseous carbon dioxide in a compressor-condenser-evaporator refrigerating system a portion of the hot gaseous refrigerant discharged by the 5 compressor may conveniently be directed in heat exchange relation with the solid carbon dioxide and such an arrangement is illustrated in the drawing. The particular apparatus shown embodies a. refrigerating machine including as its principal elements compressor ll,.a condenser ll, andan evaporator l2, all connected in orbital relation. Gaseous refrigerant such as carbon dioxide is compressed by the reciprocating type compressor II, which includes a cylinder 13 and reciprocable piston l3 driven by a suitable prime mover (not shown). The compound gaseous refrigerant is discharged therefrom through a suitable exhaust valve ll into an outlet conduit l4. The gaseous refrigerant passes through the conduit I4 and a conduit IE to the condenser H. In the case of a carbon dioxide refrigerating machine the gaseous refrigerant is ordinarily discharged from the compressor at a pressure of approximately 1000 pounds per square inch and a temperature of from 200 to 240? F. The hot compressed gaseous refrigerant flowing through the condenser" H is condensed by the transfer of heat therefrom to a cooling medium in the condenser. The particular condenser shown is of the water cooled type, water being circulated through a casing l6 froman inlet lGlto an outlet l6 over the surfaces of a helical refrigerant coil I! and in heat exchange relation therewith, the refrigerant 35 being liquefied by the transfer of heat to the cool- Y tinued until the temperature of the zone in which the evaporator I2 is located sired value. Refrigerating machines of the type described are frequently used in air-conditioning installations for large public buildings as well as in refrigerating plants of various sorts, because of the non-toxic character of, the refrigerant. In all such installations varying amounts of leakage of '53 is reduced to a dethe gaseous refrigerant will be had. This leakage ordinarily occurs in'relatively small quantities at the compressor piston valves and various pipes or conduit joints. In addition, there is greater like- 'bon dioxide as a reserve sourceof refrigerant since even though the material may be had much more cheaply in this form, no method nor ap-' paratus has heretofore been available for quickly converting solid carbon dioxide into gaseous form. Thus, if a quantity of say 75 pounds of solid carbon dioxide is confined in a metal tank at ordinary room temperature, it will require approximately twelve hours for it to sublime or change into gaseous form. Although such a slow conversion rate might be adequate for supplying smallreplenishments to a refrigerating system, it would be altogether unsuited to take care of an emergency condition in which a large: portion of the original charge of gaseous carbon dioxide in the refrigerating machine had been lost. The present invention contemplates a method and apparatus for; converting solid carbon dioxide from solid to gaseous form almost instantaneously so that it will be readily available whatever the character of the condition requiring its use. q A

In the apparatus shown in the drawing, a reserve supply of carbon dioxide in the form of solid blocks 2| is contained in a hermetically sealed cylindrical metal .tank or container 22. This tank may conveniently be supported adja cent the refrigerating machine which it is adapted to supply. A portion of the hot gaseous re- 'frigerant discharged from the compressor III 'is circulated in heat exchange relation with the blocks of solid carbon dioxide 2| within the container 22. Thus, a by- -pass conduit 24 directs a portion of the compressed gaseous carbon dioxide from the conduit l4 to the interior of the container 22. A manually operable valve :25 is provided at the juncture of the conduits 244 and I4 in order to control the flow of gaseous refrigerant through the conduit 24. This valve simply opens and closes the inlet of the conduit 24 and does not obstruct the flow of--'fluid through the conduit' l4. The solid carbon dioxide is ordinarily at a temperature of approximately 7'7 below zero F. while the compressed gaseous carbon dioxide supplied through the conduit 24 enters the container at a temperature of approximately 200 F. This hot gaseous carbon dioxide circulating in contact with the solidcarbon dioxide quickly converts it into gaseous forms This action is enhanced by the speed of flow of the comtively low heat conductivity.

Upon conversion of the solid carbon dioxide in the container 22 to gaseous form, the pressure in the container attains. a value of approximately 900 pounds per square 1110]],12116 volume of the container being of the same order of magnitude as that of the original filling of solid carbon dioxide. The gaseous carbon dioxide thus formed as well as the gas supplied to the container 22 from the compressor is returned. to the refrigerating system through a conduit 26. This conduit 26 communicates with the intake conduit 20 of the compressor l0 througha manually operable valve 21. This valve controls only the flow of fluid in the conduit 26 and not the flow in conduit 20. A manually operable valve 23 may also-conveniently be-located at the outlet of the container 22. In some cases, the solid carbon dioxide withinv the container 22 may be converted to liquid rather than to gaseous form. The pressure at the intake ofthe compressor III is ordinarily of the order of about'400 pounds per square inch as compared to the pressure of900 pounds per square inch in the container 22, however, so that any liquid carbon dioxide flowing through the conduit v26 expands rapidly as it passes through the valve 21 into the conduit 20 and thus is converted into gaseous form. The flow of gas through the conduit 20 during the normal operation of the refrigerating machine carries away any frost formed at the valve '21 during this expansion and thus prevents clogging of the same.

It will thus be seen that a by-pass is provided between the high and low pressure sides of the refrigerating machine or system, these high and low pressure sides being separated by the expansion valve l9. In the apparatus shown the bypass is formed byconduit 24, container 22 and conduit 26, and serves to direct hot'gaseous carbon dioxide in heat exchange relationawith the supply of solid carbon dioxide. 0

In the operation of the apparatus described above, the operator of the refrigerating machine is apprised of any loss of carbon dioxide in the machine by the usual gauges or other measuring devices. In case there is such a loss and the necessity for replenishment of. the charge thus arises, the valve 25 is first opened.. Upon such opening of the valve 25, gaseous 'carbon dioxide is supplied to the interior of the container 22 through the conduit 24'at a relatively high pressure and temperature. The solid carbon dioxide into gaseous form as described above. After such conversion the valve 21 is opened, thus admitting the desired quantity of gaseous carbon dioxide to replenish the charge in the machine. The conversion of carbon dioxide from solid to gaseous form takes place so rapidly in the improved apparatus that the valve 21 may be opened as soon as the operator has completed opening of the valve 2 6. After all of the solid carbon dioxide within the container 22 has been converted into gaseous form, the valves 26 and 21 may be closed and the container 22 refilled through a suitable aperture in the top of the container which is normally closed by a gas tight cover plate 28.

Although a particularflm cation and embodiment of the inyention have been shown and described in some detail for the P p ses of illustration, the inventionv is notlimited to such particular application and embodiment but on the other hand, the appended claims are intended to cover all modifications within the spirit and scope of the invention. v v

I claim as my invention: 1. 1118 method of replenishing a charge of gaseous carbon dioxide in a"comp'ression-condensing-expansion cycle refrigerating machine, which comprises, sequentially compressing, conwithin the container 22 is then rapidly converted 4 I densing and expanding a charge of carbon dioxide in a refrigerating cycle, circulating a portion of the hot compressed gaseous carbon dioxide in direct surface contact with a portion of solid carbon dioxide after' the compression stage and prior to the condensation stage, mainthe machine.

3. The method of operating a refrigerating taining the gaseous and solid carbon dioxide coritinuousiy-under pressure, and returning the resulting gaseous carbon dioxide as well as such portion of the compressed gaseous carbon dioxide to the original charge.

2. The method of replenishing a charge of gaseous carbon dioxide in a compression-condensing-expansion cycle refrigerating machine, which comprises, sequentially compressing, condensing and expanding a charge of carbon dioxide in a refrigerating cycle, circulating a. por-' tion of the hot compressed gaseous carbon dioxide in heat exchange relation with a portion of solid carbon dioxide after the compression stage and prior to the condensation stage, and introducing the resulting gaseous carbon dioxide as well as such portion of the compressed carbon dioxide into the expanded carbon dioxide in .verted carbon dioxide to type refrigerating machine having high and low pressure sides containing a charge of carbon dioxide which comprises by-passing a portion of the carbon dioxide from the high pressure to the low pressure side of the machine, circulating the carbon dioxide in heat exchange relation with a portion of solid carbon dioxide, and introducing the gaseous carbon dioxide derived from the solid carbon dioxide into the low pressure side of the machine.

5. The combination of a refrigerating system having high and low pressure sides and adapted to contain a charge of carbon dioxide, means for by-passing a portion of the charge from said high pressure side to said low pressure side, means for confining a quantity of solid carbon dioxide in heat exchange relation with the portion of the charge flowing through said bypass means, and means for introducing gaseous carbon dioxide derived from the solid carbon dioxide into said low pressure side of said system.

6. A refrigerating apparatus comprising, in combination, a compressor, a condenser, and an evaporator connected in orbital relation and adapted to contain a charge of gaseous carbon dioxide, means including a hermetically sealed container for confining a portion of solid carbon dioxide as a reserve supply for the charge in the apparatus, means operable at will for by-passing a portion of the compressed gaseous carbon dioxide discharged from said compressor through said container to convert the solid carbon dioxide contained therein into gaseous form, and means for conveying a regulated quantity of the consaid compressor.

ROY E McIIRA'II-I. 

